Transmission of blue (S) cone signals through the primate lateral geniculate nucleus.
This study concerns the transmission of short-wavelength-sensitive (S) cone signals through the primate dorsal lateral geniculate nucleus. The principal cell classes, magnocellular (MC) and parvocellular (PC), are traditionally segregated into on- and off-subtypes on the basis of the sign of their response to luminance variation. Cells dominated by input from S-cones ('blue-on and blue-off') are less frequently encountered and their properties are less well understood. Here we characterize the spatial and chromatic properties of a large sample of blue-on and blue-off neurons and contrast them with those of PC and MC neurons. The results confirm that blue-on and blue-off cells have larger receptive fields than PC and MC neurons at equivalent eccentricities. Relative to blue-on cells, blue-off cells are less sensitive to S-cone contrast, have larger receptive fields, and show more low-pass spatial frequency tuning. Thus, blue-on and blue-off neurons lack the functional symmetry characteristic of on- and off-subtypes in the MC and PC pathways. The majority of MC and PC cells received no detectible input from S-cones. Where present, input from S-cones tended to provide weak inhibition to PC cells. All cell types showed evidence of a suppressive extra-classical receptive field driven largely or exclusively by ML-cones. These data indicate that S-cone signals are isolated to supply the classical receptive field mechanisms of blue-on and blue-off cells in the LGN, and that the low spatial precision of S-cone vision has origins in both classical and extraclassical receptive field properties of subcortical pathways.
Tailby
C
C
National Vision Research Institute of Australia, Corner of Keppel and Cardigan Streets, Carlton, Victoria 3053, Australia.
Szmajda
B A
BA
Buzás
P
P
Lee
B B
BB
Martin
P R
PR
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002144:Callithrix / Q000502:physiology*; D003118:Color Perception / Q000502:physiology*; D015350:Contrast Sensitivity / Q000502:physiology; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D005829:Geniculate Bodies / Q000166:cytology / Q000502:physiology*; D008297:Male; D009433:Neural Inhibition / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000502:physiology; D010775:Photic Stimulation; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology; D014794:Visual Fields / Q000502:physiology